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Full text of "Treatise On Applied Analytical Chemistry(Vol-1)"

POTASSIUM HYDROXIDE

87

silica, alumina and ferric oxide) and in proportions.   The tests made are
as follows :

1.  Solubility.—10 grams with 20 c.c. of water should give a clear,
colourless solution.    Any insoluble residue (silica, ferric oxide, etc.) may
be filtered off and weighed.

5 grams dissolved in 10 c.c. of water and treated with 25 c.c. of 95%
alcohol, should give a clear, homogeneous solution, which does not separate
into two layers on standing (carbonates and other salts).

2.  Chlorides.—2 grams are dissolved in water, acidified with nitric
acid and made up to 60 c.c.; silver nitrate should then cause only a faint
opalescence.

3.  Sulphates.—3 grams are dissolved in 50 c.c. of water, acidified with
hydrochloric acid, boiled and treated with barium chloride.   Any turbidity
or p/ecipitate formed after an hour is observed.

4.  Nitrates.—2 grams are dissolved in water, neutralised with sulphuric
acid and diluted to 25 c.c., this solution being poured carefully into a test-
tube containing 10 c.c. of cone, sulphuric acid with a few crystals of diphenyl-
amine : any blue coloration formed at the zone of contact of the two liquids
within a few minutes is noted.

5.  Carbonates.—>2 grams are dissolved in 10 c.c. of water and the
solution poured into  dilute  (i : i)  hydrochloric acid, any effervescence
being observed.

6.  Phosphates.—5 grams, dissolved in water and acidified with nitric
acid, are treated with ammonium molybdate and gently warmed :   the
formation of a yellow precipitate within about two hours is noted.

7.  Silica.—5 grams are dissolved in dilute hydrochloric acid, the liquid
evaporated to dryness, the residue heated at 105°, and taken up in water
again :   gelatinous flocks separate after some time if silica is present.

8.  Alumina.—5 grams are dissolved in dilute acetic acid, a slight excess
of ammonia being added and the volume made up to 100 c.c. with water:
the deposition of gelatinous flocks immediately or within about two hours
indicates alumina.

9.  Heavy Metals.—5 grams, dissolved in slight excess of dilute hydro-
chloric acid, are treated with hydrogen sulphide and any turbidity noted,
either before or after addition of excess of ammonia.

10.  Sodium.—The solution in hydrochloric acid is tested in the Bunsen
flame.

11.  Ammonia.—2-3 grams are dissolved in water and the solution
tested with 2-3 drops of Nessler solution.

12.  Quantitative   Determination.—The   total   alkalinity   and   the
alkalinity after treatment with barium chloride are determined with methyl
orange as indicator, the amounts of potassium hydroxide and carbonate
being thus obtained,  i c.c. N-acid — 0-056 gram KOH or 0-069 g^111 K2COa.

The determination of the various impurities is carried out by methods
similar to those indicated under " Sodium Carbonate " (q.v.).

*
* *

The best potassium hydroxide is that termed " by baryta " ; then come that
by alcohol" and that "by lime."tion with silver